1. Field of the Invention
The present invention pretains to a storage box for wafer cassettes, and more particularly, pertains to a standard mechanical interface (SMIF) storage box, including a box, box door, and locking clips for encompassing a wafer cassette.
2. Description of the Prior Art
The SMIF box, SMIF standing for Standard Mechanical Interface equipment, is an industry-wide uniform interface for transferring a wafer cassette carrying a plurality of silicon wafers between boxes or into and out of processing equipment. The SMIF box provides a clean room environment for the wafers inside the boxes, as well as equipment canopies isolated from an operator's environment. The group which designated the standard specifications for SMIF designed an entirely new system, as well as dictating specifications requiring a new design for the SMIF box, box door, and locking mechanism.
The prior art boxes have not been acceptable to robotic processing equipment, and also have not provided the necessary wafer environment inside the storage boxes. Prior art storage boxes have not been compatible nor oriented for robotic processing equipment, especially state-of-the-art robotic processing equipment for handling of wafer cassettes, including cross-bar wafer cassettes in storage boxes, such as that designed under the SMIF concept.
U.S. Pat. No. 4,582,219, entitled "Storage Box Having Resilient Fastening Means" issued Apr. 15, 1986, assigned to the assignee of this patent is representative of the SMIF box and for the basis of this patent.
Prior art boxes have not fully provided for spring loaded or tensioned securement and cotnainment of wafers in a wafer cassette contained within a SMIF box. Containment methods were of a fixed type calling for much more precise fit of the containment devices against the wafers.
The present invention overcomes the disadvantages of the prior art by providing a wafer retainer spring contained in a storage box designated for use in standard mechanical interface (SMIF) equipment for processing and containment of wafers held in a wafer cassette, the wafer cassette being housed in the SMIF storage box.